More late-night clashes in Ferguson

FERGUSON, MO - Police and protesters are again in a tense standoff in Ferguson, Missouri, more than a week after an unarmed black teenager was shot and killed by a white police officer.

Monday night, police used bullhorns to order the crowds to leave, and noisemakers and armored vehicles were used to push back demonstrators. During one confrontation, police fired tear gas and flash grenades. National Guard units were sent to Ferguson Monday, but most of them have been keeping their distance.

Crowd control has remained the responsibly of police, with most of the National Guard units that had been summoned by Gov. Jay Nixon keeping their distance from the protests and protecting a police staging area.

President Barack Obama says he spoke to Gov. Nixon about his deployment of the National Guard in Ferguson and urged the governor to ensure the Guard was used in a limited way.